End fitting for vapor arc lamps



Nov. 16, 1954 F. CLARK 2,694,774

END FITTING FOR VAPOR ARC LAMPS Filed April 19, 1950 T i j. 10 10' 15 22 20 '2'2 INVENTOR.

FRANKLIN CLARK ATTORNEY United States Patent END FITTING FOR VAPOR ARC LAMPS Franklin Clark, Chatham, N. J., assignor to Hanovia Chemical and Mfg. Company, Newark, N. 1., a corporation of New Jersey Application April 19, 1950, Serial No. 156,901

3 Claims. (Cl. 24011.4)

The present invention deals with an end fitting for vapor arc lamps and'more particularly with an end fitting for vapor arc lamps of the type employed in the printing of photo-sensitive surfaces, e. g. in blue printing machines.

Vapor arc lamps of the type employed in blue printing machines, e. g. lamps which are characterized by a considerable increase in vapor pressure after ignition, produce elevated temperatures which are detrimental in blue printing machines and a cooling means must be provided to lessen these high temperatures. Cooling drafts or air currents are generally employed for this purpose. However, since an unprotected lamp operating at a voltage high enough to provide maximum efficiency is sensitive to drafts or air currents, a protective envelope is resorted to or else the mercury vapor will condense and cause a drop in voltage and a consequent reduction in lamp wattage. Protective light transmissive envelopes for this purpose are well known in the present art.

it is desirable to provide the type of lamps above described, including said protective envelope, as a unit and, therefore, an end fitting is required to support the lamp unit structure. In providing such end fittings, the ex pansion and contraction of the outer or protective envelope must be considered. Since the burner envelope, e. g. the quartz envelope containing the discharge, is not subject to an expansion comparable to that of the outer envelope, the quartz envelope must be mounted internally of but independently of the outer envelope. For example, the quartz envelope is usually mounted by means allowing a substantial freedom of movement along the lamp axis to allow for expansion of the outer glass envelope. It is desirable to support the burner envelope with a metal support for maximum strength and at the same time to allow a slidable movement between a ferrule covered end portion of the lamp and the metal support.

However, it has been found that the metal support, after the lamp has been in operation for a while, conducts excessive heat to the burner seal at the end of the quartz tube which is detrimental to the life of the burner.

It is an object of the present invention to provide an end fitting which as a single unit supports an end of an outer envelope and an end of the quartz arc tube contained therein. It is another object of the present invention to provide an end fitting containing a metal support for the arc vessel and which support does not produce excessive heat at the end of said arc vessel. It is a further object of the present invention to provide a vapor arc discharge device comprising an end fitting of simple structure easily assembled and disassembled. Other objects and advantages of the present invention will become apparent from the description hereinafter following and the drawings forming part hereof in which:

Figure 1 is a side view of a lamp assembly according to the present invention shown partly in section and partly in elevation,

Figure 2 is a side view of the embodiment shown in Figure 1,

Figure 3 illustrates a cross-sectional view of an end fitting including a lamp supporting disc as a modification of the present invention.

According to the present invention, an end fitting is provided which permits a lamp assembly, e. g. a lamp assembly or vapor arc discharge device of the type employed in blue printing machines, to be manufactured as a unit and which includes self-contained structures for operation independently of parts of the apparatus, e. g. blue 2,694,774 Patented Nov. 16, 1954 ICC printing machine, to which the lamp assembly is applicable. For example, the lamp assembly of the present invention need only be secured internally of a blue printing machine and plugged into or otherwise electrically connected to electrical terminals contained in said machine. Since the lamp is manufactured as an independent unit, it possesses a flexibility of use because the end fittings completely enclose all end structures which enable the lamp to operate with maximum efficiency.

Figure 1 illustrates a tubular quartz vapor arc lamp envelope 1 containing an inert gas, mercury 2, electrode 3, and having an end thereof capped by a ferrule 4, said ferrule extending from the end of the arc lamp envelope to a portion thereof forward of the electrode 3. The ferrule 4 is seated within an end portion 5 of the tubular metal support 6 which is formed of a major portion 7 of larger diameter than the minor portion or end portion 5. The major portion 7 is contained within a cylindrical cavity or bore 8 of an electrically non-conductive or ceramic end closure 9, said major portion containing an enclosed lead-in conductor 10, electrically connected to the lamp electrode 3 and through an end wall of the closure 9 to a terminal contact 10 or a source of current, and the hermetically sealed terminal 11 of the envelope 1. The ceramic end closure 9 is substantially cup-like and is provided with a rim or flange 12 having an overall diameter substantially equal to that of a tubular outer glass envelope 13 which encloses the quartz or discharge envelope 1, and which may be opaque to unwanted radiations. The tubular glass outer envelope 13 is mechanically connected to the flange 12 of the ceramic end closure 9 by means of a metal sleeve 14, said sleeve being turned over the flange 12 to provide a groove 15 between the end of the outer envelope 13 and the flange 12, said groove providing a stop to space the envelope 13 from said flange. The sleeve 14 is slotted to provide pronglike members 16 extending therefrom, said prongs being heat insulated from the envelope 13 by means of an insulating material, e. g. asbestos 17, which is preferably cemented to the envelope 13 by, for example, sodium silicate. Having positioned the sleeve 14 over the envelope 13, I mechanically secure the prong-like members around the end of said envelope by means of at least one metallic strip 18 and preferably two such strips, said strips being drawn tightly around said prongs and locked thereon by retaining means 19, e. g. retaining means such as a bolt and nut, which also secures said strip to a retaining plate 20. The retaining plate 20 is provided with an elongated slot 21 formed therethrough and parallel to the envelope 13, said slot containing a spool-like member 22 having an axial bore through which said spool-like member is secured to an appropriate apparatus. It is apparent that the spool-like member is secured in fixed relation to the apparatus, e. g. blue printing machine, and upon expansion of the glass envelope 13, the end fitting is caused to move laterally within the limits of the slot 21.

Figure 2 illustrates particularly the metal support for the end of the arc vessel 1, as above described, and which metal support is slotted along its entire length so as to be adjustable with respect to the diameter of the bore 8 and the diameter of the ferrule-capped end portion of the quartz envelope 1. In some instances, depending upon the temperature at which the lamp operates, the sealed end 11 of the envelope 1 may be detrimentally subjected to excessive heat and I, therefore, provide a heat insulating disc support 23 according to Figure 3 which reduces the heat at the sealed terminal 11 and safeguards said sealed terminal from excessive heat.

The disc support 23 consists of insulating material centrally apertured and is preferably reinforced for rigidity by cooperating circular metal plates 24 and 25 secured to the faces thereof by a retaining means 26, said disc support being seated or positioned into an annular seat 27 formed into the open end of the end closure 9.

It is apparent from the preceding disclosure that in the event of a detective quartz arc vessel, it is quite a simple task to remove the unit assembly from, for example, a blue print machine, disassemble the unit, replace the arc vessel, and assemble the unit for placement into said blue printing machine.

What I claim is:

1. In a vapor arc discharge device thecombination comprising an inner tubular quartz enclosed vapor arc lamp, an outer tubular protective glass envelope therefor for the prevention of condensation of mercury vapor due, to ambient, air currents, and at least one end fitting struc ture mounted on and supporting the end portion of both the lamp and the envelope, said fitting including a metal ferrule mounted on the end of said tubular lamp and extending forward of an electrode contained therein, a cup like closure member of an electrically non-conductive material having an inner cylindrical cavity and an outwardly extending flange at its open end, a supporting means seated within said cavity and within which an end of said lamp is supported, said cavity enclosing a lead-in conductor extending through a hermetically sealed terminal projecting axially outwardly from the end of the lamp, said lead-in conductor being electrically connected to an electrode Within said lamp and through the cup-like end, of said closure member to a. source of current, a metal sleeve secured over the flange of said closure member and slidably fitting over an end of said; outer envelope, said sleeve being bent into a grooved stop portion between the end of the outer envelope and the flange, ametallic binding strip mechanically secured around said sleeve and over an end portion of said outer envelope, said strip being secured to a retaining plate having, an elongated slot formed therethrough and parallel to saidenvelope, said slot containing a spool-likemember having an axial bore through which said spool-like member is secured, whereby said base retaining plate is laterally moveable upon expansion of said glass envelope due to heat gen erated during the operation of said lamp.

2. The vapor arc discharge device means of claim 1 whereinsaid supporting means consists of a tubular metal support member extending outwardly from said ferrule, and in which said ferrule is seated, the support member being seated within said cavity to support said lamp, the ferrutlle support member being slotted along its entire lengt 3. The vapor arc discharge device means of claim 1 wherein said supporting means consists of a centrally apertured insulating disc member reinforced by a cooperating metal plate secured to a face thereof mounted on said terminal end and seated into an annular seat formed on the inner surface of the open end of said cuplike closure member.

References; Cited in the file of, thispatent UNITED STATES PATENTS Number Name Date;

1,838,508 Wantz Dec. 29, 1931 2,009,203 Pirani, July 23, 1935 2,135,696 Baumhauer Nov. 8, 1938 2,194,300 Found Mar. 19, 1940 2,363,109 Keiffer Nov. 21, 1.944 2,457,353 Davis Dec. 28, 1948- 2,515,747 Vaughan July 18, 1950 FOREIGN PATENTS Number Country Date 428,925 Great Britain May 21, 1935 428,996 Great Britain May 22, 1935 445,648 Great Britain Apr. 16, 193.6 

